Distances can be measured between a measuring device and an object without a physical contact between the device and the object by optical methods. In these methods, the object is illuminated by the device and the light back-reflected from the object is then captured by a light detector of the device.
Distances can for example be determined by periodically modulating the light intensity which is emitted from the device and by measuring the phase difference between the emitted light and the back-reflected light arriving on the detector. However, due to the periodicity of the light intensity, this method results in an ambiguous distance measurement. Unambiguous distance measurements can be determined by measuring the time of flight between the emission of light and the arrival of the back-reflected light on the detector.
Conventional distance measurements are carried out by measuring a property of the light, in particular the intensity, as a function of time. Then a plot of the property versus the time is processed in order to obtain the time of flight. This processing can be computationally complicated and can therefore require a long time to be performed. If a distance measurement needs a long time to be performed, this can cause a reduction of the repetition rate for taking the distance measurements.
The precision of the conventional distance measurements is limited by the size of the time steps, with which the property of the light is measured. Also, for the conventional distance measurement, different reflectivities of the object can lead to different shapes of the plot. When processing a different plot, this can lead to a different distance, so that the distance depends on the reflectivity of the object, which further decreases the precision for the conventional distance measurements.